Home – Home – Jornals – Thermophysics and Aeromechanics 2009 number 1

The computer model of the initial stage of condensation processes is developed. The stochastic processes of adsorption, surface diffusion, and desorption occur on the 70×70 lattice of adsorption vacancies. The model was tested by an example close to water vapor sorption on a conventional crystal surface. Computed results demonstrate the processes of nucleation, growth of crystals, and developed condensation. Computations were carried out for various adsorption energies. Results showed that with decreasing energy of adsorption the character and rate of nucleation and subsequent condensation vary. With decreasing energy of adsorption the probability of nucleation of islets on substrate reduces, the filling of the next atomic layers on islets occurs earlier than the filling of the substrate, the growth rate of islets in height increases as compared to condensation of a continuous film, and the growth rate of area of islets decreases. There is a typical energy of adsorption at which the growth rate of islets in height reaches its maximum. At a further drop of adsorption energy, there is a growth of islets only in height, the growth rate, however, reduces. The phenomena revealed in computations illustrate the mechanism of origin of columnar and filamentary crystals.